Near field communication (“NFC”) devices are capable of communicating when they are placed in close proximity to each other, and may be used for transactions such as payment transactions. Each of the NFC communication devices includes an antenna and related circuitry such as a matching circuit. A first NFC communication device generates a wireless carrier signal at a suitable frequency such as 13.56 MHz and transmits that signal over its antenna. When the antenna of a second NFC communication device is placed in close proximity to the antenna of the first NFC communication device, the two devices become inductively coupled, such that energy is coupled between the two devices through a shared magnetic field.
When the two NFC communication devices are inductively coupled, either of the NFC communication devices may communicate via modulated versions of the wireless carrier signal. The first NFC communication device may modify aspects of the wireless carrier signal such as amplitude, frequency, and phase prior to transmission in order to encode data that is transmitted to the second NFC communication device. During times that the first device is not transmitting, the second NFC communication device may encode data that is transmitted to the first NFC communication device. The second NFC communication device modifies the inductively coupled signal using techniques such as active or passive load modulation. The first NFC communication device receives the encoded data based on the changes to the inductively coupled signal.
The use of NFC for payment transactions requires the antenna of the customer's NFC-capable payment device to be placed in close proximity to the antenna of the merchant's NFC-capable payment terminal in order to inductively couple the NFC communication devices for the exchange data between the two NFC communication devices. However, the antenna of the merchant's NFC-capable payment terminal may have several locations with very weak mutual coupling capabilities. The locations with weak coupling capabilities can be referred to as “dead zones” and can correspond to areas where the magnetic flux of the magnetic field produced by the antenna of the merchant's NFC-capable payment terminal is reduced as a result of the configuration of the antenna and/or the relative positions of the customer's NFC-capable payment device and the merchant's NFC-capable payment terminal. When the customer's NFC-capable payment device is located in one of the “dead zones,” the merchant's NFC-capable payment terminal may not be able to inductively couple with the customer's NFC-capable payment device, thereby preventing or limiting the exchange of data between the merchant's NFC-capable payment terminal and the customer's NFC-capable payment device.